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4-nitrophenol (4-NP) is considered to be a harmful solid waste because of its toxicity and persistence. It is categorised as a priority contaminant by the United States environmental protection agency. In this work, we present a simple, easy and comprehensive electrochemical investigation of the electrocatalytic reduction of 4-NP in Britton-Robinson buffer solution as the supporting electrolyte at the surface of zero-valent silver electrode (ZVAgE). Different electrochemical methods such as cyclic voltammetry, chronoamperometry, electrochemical impedance spectroscopy, and Tafel plots were used to evaluate heterogeneous kinetics and illustrate the reduction mechanism of 4-NP. The experimentally determined parameters confirm that ZVAgE has a significant electrocatalytic activity towards 4-NP electro-reduction as compared to glassy carbon electrode (GCE). Under optimal conditions, the detection of 4-NP was found to have a low detection limit of 3.03 × 10−7 mol L−1 in the range from 8.0 × 10−6 to 1.0 × 10−4 mol L−1. Additionally, the sensor was successfully applied in the determination of 4-NP even in the presence of other common electroactive interference and real samples analysis (wastewater and river water samples). Therefore, the proposed method is simple, rapid, stable, sensitive, specific, and cost-effective and can be applicable for real sample detection. [ABSTRACT FROM AUTHOR]

The present research

In this paper, a simple chemical method is reported for the synthesis of silver nanoparticles using β‐1,4 poly D‐glucosamine as stabilizer agent and their application towards electrocatalytical determination of p‐nitrophenol (p‐NP). The formation of β‐1,4 poly D‐glucosamine capped silver nanoparticles was confirmed using UV‐Vis spectroscopy, Scanning Electronic Microscopy (SEM), and Fourier Transform Infrared (FTIR) spectroscopy. The electrocatalytic activity of the β‐1,4 poly D‐glucosamine capped silver nanoparticles modified graphite carbon electrode (β 1,4 p‐DGA‐AgNPs/GrCE) towards p‐NP was studied using cyclic voltammetry (CV), AC electrochemical impedance spectroscopy (EIS), and amperometric (i–t) studies. Typically, the obtained results were compared with those for unmodified graphite carbon. The results clearly reveal that the end prepared sensor has high electrocatalytic activity for p‐NP reduction. From the DPV results, (β 1,4 p‐DGA‐AgNPs/GrCE) was concluded as viable sensor for the electrochemical determination of p‐NP in a linear range from 1.0×10−6 to 1.0×10−4 mol L−1. The minimum calculated concentration that can be detected by the proposed electrode is 6.0×10−7 mol L−1 in terms of the detection limit ((3×σ)/P). [ABSTRACT FROM AUTHOR]

A sensitive, selective and reproducible electrochemical method has been established for the electroanalysis of 4-nitroaniline (4-NA) using a carbon paste electrode modified with a chitosan solution gelled in acetic acid (CS@CPE). The modified electrode was then characterized spectroscopically using Fourier Transform Infrared (FTIR) spectroscopy. In addition, the electrochemical and interfacial characteristics of the as-prepared modified electrode were assessed by potentiodynamic cyclic voltammetry (CV) and AC electrochemical impedance spectroscopy (EIS). Differential pulse voltammetry (DPV) was additionally used to deduce the trace amounts of (4-NA) in phosphate buffered saline (PBS) of pH 7.0 as an ideal electrolyte. Under optimized conditions, the peak current of 4-NA increased linearly with the increasing 4-NA concentration over the range of 0.1 μM to 0.1 Mm. The calibration curve presents two linear ranges of current versus 4-NA concentration with a detection limit of 93.4 nM (3sb / B). The repeatability of the current peak registered at CS@CPE was performed at a level of 0.5 μM 4-NA employing one sensor on the same day for eight measurements. The relative standard deviation was 3.5%. Unlabelled Image • CS@CPE was used to detect 4-nitroaniline by differential pulse voltammetry. • All experimental parameters that affected 4-NA detection were optimized. • The results indicated the feasibility to determine 4-NA in wastewater. [ABSTRACT FROM AUTHOR]

In the present study, the proposed sensor was prepared by silver microparticles-impregnated carbon paste electrode (Ag-CPE) and used for electrocatalytic reduction of 4-nitroaniline (4-NA). The effect of the amount of silver into carbon paste on the peak potential shift was investigated. Electrochemical impedance spectroscopy (EIS) analyses were realized in the presence of [Fe(CN) 6 ] 3− / 4− and KCl as a redox probe. The cell-electrolyte resistance (R s ), charge transfer resistance (R et ), and electron-transfer rate constant (k app ) were calculated for different modified electrode. The electrocatalysis of 4-nitroaniline by silver microparticles as a redox was studied in aqueous media at the surface of a carbon paste electrode using cyclic voltammetry (CV) and chronoamperometry methods. In addition to that, the Ag-CPE exhibits excellent electrocatalytic activity indicating that the modification with silver can greatly accelerate the electron transfer. The catalytic rate constant and diffusion coefficient for 4-nitroaniline were found to be 1.36 × 10 −2  mol −1  L s −1 and 3.35 × 10 −6  cm 2  s −1 respectively. [ABSTRACT FROM AUTHOR]

The present work reports on electrocatalytic activity of silver electrode for 4-nitroaniline (4-NA) reduction, where its performance is compared with conventionally used electrodes (gold, graphite and glassy carbon). The voltammetric behavior of 4-nitroaniline (4-NA) is explored where a sensitive cathodic peak has appeared at about − 0.26 V (vs. Ag/AgCl/3 M KCl) in Britton Robinson buffer solution (pH 2.0). This peak results from the irreversible reduction of 4-NA at metallic silver electrode. The catalytic effect was evaluated using cyclic voltammetry and chronoamperometry. Indeed, the cathodic transfer coefficient was 0.57 and electron transfer rate constant was evaluated to be 7.38 × 10 − 5 cm 2 s − 1 . Electrochemical impedance spectroscopy also confirms our experimental results as the silver electrode shows least charge transfer resistance. In order to provide electrochemical detection to reducing the nitro groups of 4-NA on the silver electrode surface, the differential pulse voltammograms were used in the potential range between 0.2 V and − 1 V vs. Ag/AgCl/(sat. KCl). Furthermore, silver electrode can be used successfully to improve the detection of 4-NA at very low concentration levels with high sensitivity. The linear calibration range was from 8.0 × 10 − 9 to 1.0 × 10 − 3 mol L − 1 . The limit of detection (LOD) was found to be 4.74 × 10 − 9 mol L − 1 , while relative standard deviation (RSD) at 1.0 × 10 − 4 mol L − 1 4-NA concentration was 1.94% for eight repetitions. Then, the proposed method was applied to detect 4-NA in wastewater and drinking water with satisfactory results. [ABSTRACT FROM AUTHOR]

[Display omitted] • The AMX oxidation at (Sn–SnO 2)–NPh–CPE was catalyzed by UVs. • Electrocatalytic determination of AMX was achieved by (Sn–SnO 2)–NPh. • The detection limit obtained was 7.78 × 10–8 mol L–1. • The interferences and analytical applications were successfully realized. The (Sn-SnO 2)-NPh-CPE modified electrode at based Microparticles of tin and tin oxide scattered on natural phosphate were utilized for amoxicillin (AMX) oxidation, it was preceded by an activation phase using ultraviolet radiation (UV) as the catalytic step before its electrochemical detection. The (Sn-SnO 2)-NPh modifier was prepared via a solid-state reaction process at a high temperature of 400 °C using natural phosphate and tin dichloride. The AMX activation by UV radiation was studied using differential pulse voltammetry, chronoamperometry and electrochemical impedance spectroscopy. Thus, the results confirm that the utilization of UV radiation catalyzed AMX oxidation. It has been found that the oxidation current of AMX increases with the increasing exposure time of AMX solution to UV radiation. The results demonstrated that the activation of the AMX by UV radiation before the electrochemical oxidation is necessary for its detection at the trace level. The oxidation peak current was linear to the AMX concentration in the range 2.0 × 10−7 to 2.0 × 10−6 mol/L with a detection limit of 7.78 × 10−8 mol/L. Moreover, the designed sensing platform was successfully employed to determine AMX in tap water and wastewater samples. [ABSTRACT FROM AUTHOR]

The present work describes a simple, inexpensive and green electrochemical sensor based on natural phosphate modified graphite paste electrode (NPh–CPE) for the electrocatalytic determination of HCQ. The NPh–CPE has demonstrated a high performance toward HCQ electro-oxidation compared to unmodified carbon paste electrode in terms of oxidation current and potential. The HCQ electrochemical behavior at NPh–CPE was studied using cyclic voltammetry (CV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS). Based on the investigation results, the electrode/analyte reaction characterization elucidates the E r C i mechanism as being a typical adsorption-controlled system. The response linearity, repeatability, accuracy and detection limit (LOD) were within the literature values range. The obtained detection limits were 5.27 × 10−7 mol L−1 and 3.34 × 10−7 mol L−1 for peak 1 and peak 2 respectively. The relative standard deviation (RSD) was found to be 2.8% for 5.0 × 10−6 mol L−1 of HCQ. The real samples analysis performed on human blood and pharmaceutical tablets have yielded satisfactory results. [Display omitted] • HCQ is determined by DPV using a natural phosphate modified carbon paste electrode. • Electrocatalytic HCQ oxidation was achieved by naturel phosphate. • The electrochemical oxidation mechanism of HCQ's peak 1 and 2 was established. • CV, EIS, CA technics confirmed the E r C i system nature. • The attained detection limit is comparable with other works. [ABSTRACT FROM AUTHOR]